Matt Damon is to be a father for the third time ? to another girl.

The 'Bourne Ultimatum' star already has two daughters.

"I'm so outnumbered down here, it's crazy," the 37-year old revealed in an interview, adding that his wife Luciana was "due soon".

Damon, the father to two-year-old Isabella and nine-year-old stepdaughter Alexia, revealed the news in an interview with USA Today.

The Miami-based actor originally confirmed Luciana's pregnancy in March.

But the couple have not yet decided on a name for the impending arrival.

"We decided to wait till she's born," the 'Oceans 11' star explained.

"We're going to get a look at her and we'll probably keep debating it!"

The actor is looking forward to spending time with his new daughter.

After completing work on his new film, 'Green Zone', he's "taking the rest of the year off," he revealed.

"I'm just hanging out with my family."

He will also be kept busy with other children ? Damon is preparing to launch the US operations of a Canadian charity called One X One Foundation.

"It's about helping kids," the actor explained.

"It's not like before I was a father I was like: 'The hell with those kids.' But something does shift when you have a child of your own. It's hard not to look at every child as somehow connected to you."

Part of his responsibility is recruiting stars for events, like an October gala in San Francisco.

"I have to make calls. Sheryl Crow is going to play at one of our events," revealed the actor, who claims he was inspired by the charity work of U2 singer Bono.

"It's the easiest call in the world to make," he added. "I just tell what the charity is about, and everyone wants to do anything they can."